1. Field of the Invention
The invention relates generally to chains including rollers, and more particularly to a roller joint sealing arrangement which can be used in a chain including rollers to seal the roller joint against lubricant efflux and/or contaminant influx.
2. Reference to Prior Art
In chains with rollers that operate in potentially corrosive or damaging environments such as the environment in which traveling water screens operate, it is often desirable to protect the chain joints and particularly each roller joint from wear. As used herein the term "roller joint" will refer to the wear surface between the inner diameter surface of a chain roller and the peripheral surface of the bushing on which the roller is mounted. In traveling water screen applications a pair of chains equipped with rollers support a plurality of baskets therebetween. The chains are continuously driven along guide rails into and out of the water in an endless loop so that the baskets filter fish and debris from a water inflow. Protection against wear of the rollers and bushings can be achieved by maintaining lubricant in the roller joints.
In the past, rollers incorporated into the chains used in traveling water screen applications experienced unacceptable wear rates due to lubricant loss from the roller joints and/or entry of contaminants into the roller joints. In extreme cases, wear on the inner diameter bearing surface of a roller can result in impingement of the chain sidebars on the guide rail along which the chain travels. The rollers used in travelling water screens are sometimes made of a metal alloy high in nickel content such as monel and can be very expensive to replace. Additionally, chains used in traveling water screens include a large number of rollers and replacement of these rollers involves lengthy water screen downtime.
Chains which employ annular seals to protect joints between chain pins and chain bushings are generally well known. Examples of such chains are provided in U.S. Pat. No. 4,424,050, issued Jan. 3, 1984 to Sato and U.S. Pat. No. 4,464,151, issued Aug. 7, 1984 to Kahl.
In chains of the type which include double outer links pivotally connected to a single center link by a bushing and a pin, it is known to seat annular sealing devices in corresponding annular grooves in the center link and the outer links. This is intended to protect the joint between the bushing and the center link from dirt and grit. An example of such a chain is disclosed in U.S. Pat. No. 2,389,874, issued Nov. 27, 1945 to Searles et al.
Additionally, U.S. Pat. No. 4,795,408 discloses a roller chain link having a roller with open opposite end faces and thrust rings which are intended to fit within the open end faces to seal lubricant in the space between the roller and the bushing.